1. Field of Invention
The present invention relates to a device which will collect high quality heat vapors at the point of generation in order to increase the ability to reuse the available energy released by the dryer section of a papermaking machine and reduce the prime energy needs by other process users.
2. Description of Prior Art
It is well known that a papermaking plant is a high consumer of energy. For example, each ton of paper dried discharges heat equivalent to 3/4 of a barrel of oil. In a typical one thousand ton per day mill, this converts to a sizeable oil well approaching thirty barrels per hour. In spite of this apparent abundance of energy waste, expensive prime heat continues to be used to satisfy such menial functions as heating water and heating air. It is then a necessity to work out an efficient system to adequately recuperate and properly recycle such waste energy.
The recuperation and recycling of heat is not new and all mills use the principle in varying degrees. Different attempts have been made to recuperate and recycle the heat lost in the dryer section of a paper machine. To that effect open hoods as well as closed hoods have been placed on top of the dryer drums of the drying section of a papermaking machine. All these have their drawbacks.
As an example, the present technology is such that exhaust humidities are limited to the order of one thousand grains per pound dry air. If exhaust humidity is raised beyond the one thousand grains, there is a very good chance that the hood will sweat, dripping water onto the sheet directly or on to the travelling felt which will transfer its moisture spots to the sheet when contact is made.
This humidity condition limits the quality of the waste heat recoverable to heat water to 135.degree. F. Water at 135.degree. F., though adequate for a variety of applications, cannot satisfy the energy demands of users beyond 135.degree. F. and therefore limits the benefits of the recovery.